Connector for tubular conduits



Feb. 4, 1958 G. M. DlNNlCK 2,822,418

CONNECTOR FOR TUBULAR CONDUITS Filed Dec. 5, 1952 2 Sheets-Sheet 1 INVENTOR GEORGE M. DINNICK WWW? (06,6 ATTORNEYj Feb. 4, 1958 G. M. DINNICK 2,822,418

CONNECTOR FOR TUBULAR CONDUITS Filed Dec. 5, 1952 2 Sheets-Sheet 2 108 u np INVENTOR GEORGE M. DINNICK 2,822,418 CONNECTOR FOR TUBULAR CONDUITS George M. Dinnick, Oxon Hill, MtL, assignor to the United States of America as represented by the Secretary of the Navy Application December 5, 1952, Serial No. 324,433 1 Claim. (Cl. 17488) (Granted under Title 35, U. S. Code (1952), see. 266) This invention relates to connectors for tubular conduits and the like and more particularly to improvements in connectors for joining sections of concentric transmission lines.

Electric lines of the type here under consideration consist of a pair of coaxially disposed, thin-walled tubular members, generally of lengths that must be connected end-to-end in order to be sufficiently long to satisfy practical requirements. The walls of the outer conductor in particular are quite thin in comparison with the outside diameter of the conductor so that notches or annular grooves in the outer surface of the conductor will result in a very great diminution of the maximum tensile and compressional strengths of the outer wall. This diminution may be quite serious in those applications where necessity requires relatively high compressional and tensile working loads, such as where long sections of cable are subjected to extremes in operating or ambient temperatures.

A connecting device for such concentric lines must be both simple and rugged, so as to be suitable for use in localities removed from access to shop facilities, and also so as to be useable by relatively unskilled workmen. As these devices usually conduct radio waves, they must also provide a good electrical impedance match between sections to avoid discontinuities in the radio field Within the conductor. An example of a prior art connecting device designed for use in such applications is that shown in Patent No. 2,209,152 to H. C. Daniels. This device provides a pair of tightening or coupling nuts threaded to opposite ends of a common coupling sleeve. The coupling nuts work against thrust rings fitted around the outer conductors so that rotation of the sleeves results in an axial movement of the sections to be joined so as to provide axial compression between the matching tubular sections. The thrust rings are secured to the outer tubular conductor by means of deep annular grooves cut in the surface of the conductor; the result is a considerable reduction in the maximum compressional and tensile shearing stress that may be applied to the conductor, as mentioned above.

The coupling sleeve-thrust ring combination provides a very satisfactory, relatively simple means for joining con centric line sections but the reduction in shearing strength resulting when the thrust ring is secured to the outer conductor in the manner described in the aforementioned patent imposes a serious limitation that must be overcome before the general method of coupling can be really satisfactory. It is obvious that the thrust rings could be welded or swaged on to the outer conductor to eliminate cutting into the conductor itself, but heat deformation resulting from such operations would also seriously reduce the shearing strength of the metal, and plastic insulation often used in such lines would be destroyed. Accordingly, one object of the present invention is to provide a coupling for sections of concentric electric conductors that will preserve the shearing strength of the conductors.

, Another object of this invention is to provide a rcng,

nited States Fatent durable connection for sections of tubular conduit or concentric line that may be readily assembled by relatively unskilled workmen under field conditions.

A further object of this invention is to provide a connector for sections of concentric electric conductors that will minimize reflection losses of radio waves transmitted within the sections of concentric line.

Other objects and features of the present invention will become apparent upon consideration of the following detailed description in connection with the accompanying drawings which illustrate a preferred embodiment of the invention. It is to be expressly understood, however, that the drawings are designed for purposes of illustration only and not as a definition of the limits of the invention, reference for the latter purpose being had to the appended claim.

In the drawings:

Figure 1 is a side elevational view of a concentric line joinhconstruction made in accordance with the present invention;

Figure 2 is a transverse sectional view taken on line 2-2 of Figure 1;

Figure 3 is a longitudinal sectional view taken on line 3-3 of Figure 2;

Figure 4 is a more detailed view of a portion of Figure 3.

With reference now to Figure l of the drawings, the concentric line sections to be joined by the novel coupling unit herein described are represented at and Concentric line lilfi consists of an outer conductor M 2 and a hollow inner conductor 1%. Likewise, concentric line 200 is made up of outer conductor 62 and a hollow inner conductor 204. As has been indicated, the con ductors are tubular and concentric; they are uniformly spaced from each other by suitable solid dielectric materials, or by shorted quarter wave stub supports as shown in U. S. Navy Publication NavShips 900,028 (1944), page 2. If solid dielectric spacing material is used, as depicted by reference numerals 3th? and 296, the dielectric must be foreshortened within the conductors to provide room for the coupling components. Removing the dielectric a few inches from the end of each concentric line section will be suificient for most purposes.

Referring now to Figures 2 and 3, it can be seen that in a concentric line application inner conductors 104 and 204 are joined at their abutting ends by a small metallic, cylindrical support member 3% inserted in the adjacent ends of these conductors. Member 3% has one end thereof hollowed out and the other end thereof is closed so as to form a base section, the outer diameter of which is substantially the same as the inner diameter of inner conductor 204 so that the base section of support member 308 fits snugly into conductor 2%. Inasmuch as the inner diameters of the two inner conductors 14M and 264 may diifer slightly, and as the conductors are subjected to bending loads, it is necessary that support member 3&8 be flexible and also that its outer diameter be adjustable to some extent. To accomplish this the open end of support member 3% is slotted for about three-quarters of its length to provide a plurality of spring fingers 3%. The spring fingers 3% terminate in the base section of member 3% where the internal diameter of member 398 has been reduced to form a shoulder 312. A threaded bore 314 is tapped axially through the center of the solid end 33% and a small wedge 316 in the shape or" a truncated cone the average diameter of which is the same as the inner radius of shoulder 312, is also provided with an axial bore. Screw 313 extends through the wedge 316 and is. threaded through bore 314 so as to bring wedge 316 to bear against shoulder 312. The spring fingers 306 may be adjusted so as to fit smoothly against the inner surface of conductor 104- after the base of support member 368 has been inserted into conductors 204, as

the fingers 3% will spread apart when the wedge- 316is tightened against shoulder 312.

in coupling the outer conductors 1&2, 2%2 an internal cylindrical support ring 31? is inserted at the junction ofconductor a diameter of 3.29 to 3.31 inches has been found to be satisfactory for the ring. A number of short pressure relieving slots 32% are cut back perpendicularly to the ends of the support ring so that the ring may be easily slipped into outer conductors 1 52, 202. Slight tapers 324 are cut into the ring on the outer surtacc thereof and extend from the center of the ring almost to each end so that the outer conductors M2, 292 may he slipped over the ring. Near each end of the ring the taper is terminated so that annular contact ridges 326 are provided at the ends of the fingers 328 formed by the pressure relieving slots The purpose of the contact ridges is to provide good electrical contact between the ends of the ring and the inner surface of the outer conductors Hi2, 2:32. The support ring is of such a length as to practically abut against the solid dielectric removed as mentioned previously.

To form a strong, dependable mechanical coupling between the outer conductors 1'32 and 2&2, the adjacent ends of conductors 192 and 2% are externally threaded to receive suitable thrust rings 111i and 21%. As more carefully shown in Figure a standard 60 degree thread is cut the outer surfaces of outer conductors NZ and 2132. The thread is cut deepest at the end of the conductor and then gradualiy and progressively diminshes in depth until it is quite shallow after 6 to 10 turns. With reference to Figure numeral 1 represents the end of outer conductor 102. As can be seen, the first turn 3 of the thread, nearest the end of the conductor, is out quite deeply into the outer surface of the conductor. As the thread progresses baclc from the end of the conductor, its depth is gradually tapered, as shown by the thread-grooves 4, 5, 6, 7, 8 and 9. The reason for this construction is primarily to increase the maximum shearing strength of the outer conductor as much as possible. It has beenfound that the greatest shearing stress occurs at the last turn of the thread away from the end of the conductor, so that the smaller the depth of the thread groove is at this point, the greater will be the maximum transverse shearing stress that can be placed upon the conductor. By gradually tapering the thread so that the deepest cut is at the end of the conductor the maximum transverse shearing stress will continue to occur at the turn of the thread farthest away from the end of the conductor and a large longitudinal tensile stress may still be carried by the threads.

Tapering the thread also has another advantage that will i be brought out below.

Thrust ring 110 is internally threaded so as to have a taper which mates with the thread cut into the outer surface of the outer conductor M92 as described above. This thread, however, is slightly deeper than that in the outer conductor so as to leave a slight clearance 12 between the thrust ring and the outer surface of the outer conductor so that space will be left between the mating threads when the thrust ring is threaded on to the outer conductor.

A pair of coupling sleeves 168 and 203, the innerradius of which is the same as the outer raduis of the outer conductor, are slipped over the outer conductors before thrust rings 11%) and 210 are tightened into place. Coupling sleeve 1% overlies thrust ring 110 and has an annular flange 114 adapted to abut against the edge of thrust ring 110, and also has an externally screw-threaded portion 212 adapted to threadedly engage the screwthreaded portion of coupling nut 203. This end of coupling nut 208 also abuts against thrust ring 210. Each coupling nut is provided with flat sections generally des- 4. ignated A in Figure 2, for convenience in engaging a pipe wrench therewith to tighten orto loosen the nuts.

In assembling the parts as have been described thus far, it will be assumed that the coupling nuts 1% and 203, and thrust rings 11d and 210 have been assembled as shown in Figure 3. The long supporttrnember 3418 is slid lnto inner conductor 2%4, and screw 3% is adjusted until spring fingers 3th: slide smoothly into inner. conductor 104.

The outer conductors are slid over springfingersSZSof cyiindrical support ring 31% and are forcedltogether as far as possible. Coupling nuts 1% and 268 are; screwthreadedly engaged with the screw end of coupling nut both nuts are screwed tight in opposite directions to draw the outer conductor sections .162 and 2M; oppositely relative to one another. By virtue of the fact that it is impossible for the, ends of the outer conductors to'buck-le inwardly because of the presence of cylindrical support ring 3-19 and that it is also impossible for them to. buckle outwardly because of the bonding and restrainingactiom afforded by thrust rings 11% and Ziil, the compressional action caused by tightening nuts 1% and 2% is madeso great as to form a cold weld at the abutting ends of conductors 16:2 and 262. Thus, a very simple gas and humidity tight joint is formed between the ends. of the outer conductors 1&2 and 2 32.

As has been mentioned, the midsection of the ring;is ,of a slightly greater diameter than the inner diameter. of the conductors. As the conductors are drawn up onto the ring, the aluminum threads that mate with thrust rings. and 210are found to cold flow and the effect is that the thrust rings are cold welded to the conductor. The;

clearance 12 is filled as a result of this coldflow of the.

aluminum so that the weld is efiected not only at. the teeth of the thread, but along the entire length of the, thread between the thrust rings and the outer conductor.

It should be noted that the thickness of cylindricalsupport ring 319 is critical if it is desired that the characteristic impedance of the joint to high frequency waves be the, same as that of the concentric line using solid dielectric spacing material. As shown in the text Radio, Engineers Handbook by F. E. Terman, first edition (1942), page 174-, the characteristic impedance of a coaxial line is a function of the dielectric constant of the medium between the conductors, and also of the ratio of the inner radius( of the outer conductor to the outer radius of thev inner. conductor. Compensation can therefore be made for. a change from a solid, beaded, or spiral solid dielectric: to. air dielectric at the joint by changing the innenradiuszofc the outer conductor, or in the instant case, by adjusting. the. thickness of the cylindrical support ring.

The radial thickness and the length of thethrust rings 110 and 210 are not particularly critical; however, when the coupling nuts are tightened, both radial forces and longitudinal shearing forces are imposed on the thrust rings, so the thickness must be sufiicient to withstand the radial forces and the length must be great enough to provide sufiicient thread length to prevent longitudinal shear ing from occurring. It should also be noted that it is necessary for one end of each of the thrust rings to be quite near the abutting end of its respective tubular member in order to prevent outward fluting or flaring of the abutting ends when the coupling nuts are being tightened;

The internal and externalconductor sections and body members of the conductors are preferably made of high conductive material such as copper or aluminum. The other parts may be made of any suitable material such, for example, as brass except for the cylindrical support ring 319. It is preferable that this ring be made of Phosphor bronze because of its strength combined with good conductivity.

The invention may be carried out in specific'ways other than herein set forth without departing from the spirit and essential characteristics of the invention; the presentemwithin the meaning and equivalent range of the appended claim are intended to be embraced therein.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

In a connector for joining sections of coaxial conductors of the type wherein one conductor is positioned within the other, first and second threaded thrust rings adapted to threadedly engage respectively first and second adjacent ends of the outer conductors of said sections to be connected, each of said first and second adjacent ends having tapered threads on the outer surface thereof progressively decreasing in depth as the thread extends away from said adjacent end of the outer conductor, the thread depth at one end of said tapered thread being substantially one half the thread depth at the opposite thereof, said threaded thrust rings being adapted to mate in a contiguous manner with said respective threaded ends of said outer conductors, a rigid internal sleeve member having a tapered outer diameter which varies to a maximum diameter at the midsection thereof and being adapted to be snugly positioned within the tubular members at their point of juncture, said internal sleeve memher being of a thickness such as to maintain the characteristic impedance of the joint substantially the same as that of the sections of coaxial conductors, means operative to maintain the adjacent ends of the inner conductors in alignment, a first coupling sleeve surrounding one of said outer conductors between the associated thrust ring and the far end of said outer conductor, a second coupling sleeve surrounding the other outer conductor at a point between its associated thrust ring and the far end of said other outer conductor, each of said coupling sleeves having parts adapted to bear against the associated thrust ring and at least one of said coupling sleeves being adapted to overlie its associated thrust ring and threadedly engage the other coupling sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 135,898 English Feb. 18, 1873 1,762,191 Ober June 10, 1930 2,014,853 Ley et al. Sept. 17, 1935 2,057,242 Mautsch Oct. 13, 1936 2,209,152 Daniels July 23, 1940 2,245,419 Unke June 10, 1941 2,305,668 Bruno Dec. 22, 1942 2,567,113 Kristensen Sept. 4, 1951 2,640,095 Lewis et al May 26, 1953 

